1. Field of the Invention
The present invention relates generally to a display device. More particularly, the present invention relates to a liquid crystal display and method for fabricating same.
2. Description of the Related Art
The market of liquid crystal displays (LCDs) is growing wider and wider over various fields including office automation equipments, audio and visual equipments, and mobile equipments due to their advantage in thickness, weight and power consumption. As shown in FIG. 23, in assembly of a LCD, a housing front 49 and a housing rear 48 cooperate with each other to retain a backlight unit 33, a panel unit 32 and a rear sheet metal 37 together in fixed operative relationship. The backlight unit 33 uses a front frame 35 and a rear frame 36 to retain lamp components, which include a lamp 11, a reflector 12, an optic sheet 16, a reflector sheet 10, and a light conductive plate 9. The panel unit 32 uses a front bezel 34 to retain a liquid display panel (LCD) 1. Connected to the LCD 1 are a connecting substrate 6 and a signal processing substrate 7 via a plurality of flexible substrates 4. The flexible substrates include driver integrated circuits (ICs). The rear sheet metal 37 has mounted thereto a converter substrate 13 and an inverter substrate 14. The converter substrate 13 is provided to convert external signal for transmission. The inverter substrate 14 is provided to supply a desired level of voltage to the lamp.
In the above-mentioned LCD, the lamp components are assembled to form one unit, the display components are assembled to form another unit and the signal processing circuit substrates are assembled to form other unit. Using the housing front 49 and housing rear 48, these units are interconnected and retained in operative relationship. Using the units in assembly is closely related to varying of specification of a LCD with different user needs. Advantages of using the units include the following. Firstly, selecting units and interconnecting the selected units to meet different user needs may achieve a wide use of a LCD. Secondary, an ease and convenience of transport may be recognized if the components are manufactured at different sites function by function because the components are retained in operative relationship by frames.
The operative interconnection of the units may include not only electric connection, but also optic connection. Increased accuracy is required in alignment to provide performance as high as expected. Maintaining good display quality requires accurate alignment between the backlight and panel units 33 and 32. It is the common practice to use frames to retain them together in operatively relationship.
One example of retaining a panel unit and a backlight unit is disclosed in JP-A 11-281963 (Toshiba). According to the teaching of this laid-open publication, the backlight unit includes a frame formed with first and second protrusions for alignment of a LCD panel of the panel unit. The first and second protrusions are arranged across the LCD panel for abutting engagement with the remote sides of it with clearance. A bezel is fast on sides of the frame of the backlight unit to retain the panel unit to the backlight unit in operative relationship. The bezel is formed with a bias protrusion that bulges into clearance between the second protrusion and the adjacent sides of the LCD panel, pressing it against the first protrusion.
Another example is disclosed in U.S. Pat. No. 5,905,550, Ohgami et al (=JP-A 9-297542, Toshiba). According to the teaching of this prior reference, a panel unit is formed with attachment flanges. With a bezel, the panel unit is fixed to a backlight unit to form an assembly. The assembly is mounted by interposing the attachment flanges between a housing front and a housing rear.
With reference to FIGS. 24 to 33, the first mentioned LCD will be further described. FIGS. 24 to 33 are perspective views showing fabricating processes of the LCD. FIGS. 24 to 27 show a sequence of processes for fabricating the backlight unit 33. FIGS. 28 to 30 show the subsequent fabricating processes till completion of the LCD.
Firstly, the assembly of a backlight unit 33 is described. As shown in FIG. 24, a reflector sheet 10, a lamp 11 and a reflector 12 are inserted into a rear frame 36. With a lamp retainer rubber 11a, the lamp 11 is temporarily fixed to the reflector 12 and has a lamp cable 15. Subsequently, as shown in FIG. 25, a light conductive plate 9, a diffusion film 16b and a lens film 16a are placed on the reflector sheet 10 within the rear frame 36 one after another. The diffusion and lens films 16b and 16a form an optic sheet 16. Finally, as shown in FIG. 26, a front frame 35 cooperates with the rear frame 36 to interpose between them the backlight components, completing the assembly of the backlight unit (see FIG. 27). Couplings 39, each having a hook 36a on the rear frame 36 inserted into its mating hook hole 35a on the front frame 35, and screws 38 fix the rear and front frames 36 and 35 to each other together.
Secondly, the assembly of a display unit 31 is described. As shown in FIG. 28, the backlight unit 33 is formed with a rib 40 for aligning a panel unit 32, which includes an LCD panel 1 with flexible substrates 4 connected to connecting and signal processing substrates 6 and 7. The LCD panel 1 is placed on the backlight unit 33. Subsequently, as shown in FIG. 29, the flexible substrates 4 are bent down, admitting the connecting and signal processing substrates 6 and 7 into behind the backlight unit 33. In one case, the connecting substrates 6 may be left on a forward surface of the backlight unit 33. In another case, the connecting substrates 6 may be fixedly attached to sides of the backlight unit 33. Subsequently, as shown in FIG. 30, a front bezel 34 and the backlight unit 33 interpose between them the panel unit 32. Couplings 31b, each including a hook 35b on the sides of the front frame 35 inserted into its mating hook hole 34a, fix the front bezel 34 and the backlight unit 33 to each other together.
With reference to FIGS. 31 to 33, the subsequent fabrication processes are described. As shown in FIG. 31, the display unit 31 is turned up side down to face a display surface 32a down. Subsequently, a rear sheet metal 37, which has mounted thereto inverter and converter substrates 14 and 13 by hooks 37a and screws 41, is mounted onto the rear surface of the display unit 31. Next, as shown in FIG. 32, screws 43 are used to fix the rear sheet metal 37 onto the rear surface of the backlight unit 33. Connecting cables 42 interconnect the substrates. Lamp cables 15 are connected to the inverter substrate 14. Finally, as shown in FIG. 33, with hooks 46a inserted into hook holes 46b and with screws 47, a housing front 49 and a housing rear 48 are fixed to each other to embrace the display unit 31.
The above-described LCD involves the following problems. One problem is the difficulty in further reducing the size, thickness and weight due to the use of front and rear frames 35, 36 in forming the backlight unit 33 and the use of front bezel 34 in forming the display unit 31. Another problem is the difficulty in maintaining precision required in final assembly of each product due to accumulation of alignment errors inevitably existing in the backlight and display units.
Another problem is the increased number of fabrication processes due to additional process of retaining or embracing assembled components of each unit and additional process of interconnecting the units.
Another problem is the complicated processes that require skilled labor. As mentioned before, the following processes form the display unit 31. One process is to put the panel unit 32 onto the backlight unit 33 with its display surface 32a up. The subsequent process is to attach the rear sheet metal 37 to the display unit 31 after turning the display unit 31 through 180 degrees until the display surface 32a faces down. In addition to such complicated work, the operation to turn the display unit 31 through 180 degrees involves potential danger that the LCD panel 1 may be scratched and/or damaged.
Another problem is the difficulty in cost reduction due to increased number of components. The increased number of components poses supply and delivery problem. Besides, there is the tendency that a lead-time from arrival of components to assembly of them is long.
A need remains for a LCD and method for fabricating same without frames and/or bezel.